Background: Disease control personnel have an important role in preventing spreading of COVID-19, such as case screening, outbreak investigation, and contact tracing. This study aims to find out their protective behaviors and other associated factors with inappropriate PPE use, as well as the percentage of seropositivity by natural SARS-CoV2 infection in September 2020 during the period without any COVID-19 vaccine. Methods: This is a cross-sectional study of 172 Thai Department of Disease Control personnel, which all had done questionnaires regarding demographic data and protective behavior. The blood test was performed to find out Neutralizing antibody titer (Nab) and Enzyme-Linked Immunosorbent Assay (ELISA). Data were analyzed using descriptive statistics and binary logistic regression was conducted for identifying factors associated with inappropriate Personal Protective Equipment (PPE) use. Results: Of all 172 participants, 38 (22.1%) were Health Care Workers (HCW), 79 (45.9%) were Public Health Personnel (PHP), and 55 (32%) were Non-Health Workers (NHW). Most were female (130; 75.6%). Hand hygiene was the behavior with the highest proportion of being done every time among all participants during work (90.5%), while cleaning high-touch surface and using cashless system were done only a few or sometimes by most participants (55.9% and 56.1%, respectively). Middle age, less experience, and working as Public Health Officers, were associated with appropriate PPE use during work. Participants who had trained for PPE use at least once in the recent year practice inappropriate PPE use less than those who had not been trained, even though there were no significant differences.

After the first wave of the COVID-19 pandemic in Thailand in 2020, there was no data related to preventive behaviors against COVID-19 infection and prevalence of previous infections among frontline immigration police, which could be used to implement health promotion and adapt preventive methods in the organization. All frontline immigration police officers working at Don Mueang International Airport, Bangkok, were invited to participate in this cross-sectional study in May 2020. The objectives were to describe their preventive behaviors and determine the prevalence of antibodies against SARS-CoV-2 using conventional neutralization assays and ELISA tests. There were 201 eligible participants. All were asked to fill in a questionnaire, which asked them to disclose their preventive behaviors against COVID-19 infection. All were tested for antibodies against SARS-CoV-2 from natural infection as vaccines were not available at that time. The most practiced preventive behaviors were wearing a mask at work and wearing a mask in daily life, while taking sick leave when suffering from respiratory symptoms was the least practiced behavior. No SARS-CoV-2 antibodies were present in any participant. Reasons for not taking sick leave, when necessary, should be investigated in further qualitative studies.